The following precedence diagram shows all the activities involved in a housing project. For each activity, the most likely activity duration, the most optimistic and most pessimistic time have been given in the table (in weeks).

(1) Calculate the probability that the project can be completed in 28 weeks. Choose from answers (a, b, c, d)

(2) If we want to be 80% sure that the project will be completed on time, how long we should schedule it? Choose from answers (e, f, g, h)

(3) If we want to be 90% sure that the project will be completed on time, how long we should schedule it? Choose from answers (i, j, k, l)